The U.S. Supreme Court case of Michael Gary Barber, et al. v. J.E. Thomas, Warden in 2009 revolved around the issue of whether federal courts could adjust a prisoner's sentence for good behavior based on time served before sentencing or only after sentencing has been imposed by the court. The petitioners were federal prisoners who argued that their good conduct time should be calculated from the day they entered prison and not just from when they were sentenced, which would reduce their overall term of imprisonment significantly if granted. However, the Supreme Court ruled against them stating that under Federal law (18 U.S.C §3624(b)), credit for satisfactory behavior can only be awarded post-sentencing and cannot include pretrial detention period as it is not considered part of the sentence imposed by a judge.

In the dissenting opinion for Barber v. Thomas, Justice Breyer argued that the majority's interpretation of 18 U.S.C §3624(b)(1) was not in line with Congress' intent when it enacted the law. He contended that a prisoner should earn good time credits based on his sentence term rather than on time served, which would result in more generous reductions of prison terms and better align with Congressional goals to incentivize good behavior among prisoners. The Justice also pointed out potential practical problems arising from the majority’s reading such as administrative difficulties and unfairness between different categories of inmates due to varying lengths of sentences. Furthermore, he criticized their reliance on grammar rules over legislative history or purpose in interpreting statutory language.